Friday, January 22, 2016

Introduction to Astrophotography - Part V

My AstroTech 12" Richey-Chretien telescope with

If you've made it this far, you've survived Parts I through IV of my series on astrophotography. There are so many more topics to cover but I hope that with what I've covered you've been able to get a handle on what's involved when you start down the path of shooting celestial objects.We're about to get serious. So far I've tried to keep the equipment involved to what most would consider reasonable, especially if astrophotography is not going to be something you do regularly. But for those of you who may want to take it to the next level, this is where we will now be going. In this segment, we'll take a look at telescopes and mounts.

Learning
To Run

My friend's Takahashi TOA 130 APO Refractor on an AstroPhysics mount inside his roll-off roof observatory. The TOA 130 is considered one of the finest imaging scopes available and provides a 1000mm focal length at f7.7. AstroPhysics is considered the Mercedes Benz of astronomical equipment and its mounts are highly regarded.

My Takahashi TSA 102 4-inch refractor on a Celestron CGEM mount

Adding more sophisticated equipment such as a bigger
telescope and mount will yield larger and/or more detailed images of your targets. For
comparison, here are images of the nebulae in Orion taken through a 4”
Takahashi refractor with its 800mm+ focal length at f8 (slightly shorter and faster with the flattener) on a Celestron CGEM mount. The equipment investment is now
in the $5,000 range (new), $3,500 used, not counting the camera and accessories. Compare these to images of the same target that I posted in Part III and you can see how much tighter the images are with much more detail.

Orion's nebulae with shorter focal lengths

Horsehead and Flame Nebulae in Orion with Takahashi TSA 102

Running Man and Great Orion Nebulae with Takahashi TSA 102

Sprinting

Now let's really push the envelope. For comparison, below are examples of the the nebulae posted above but through my 12” AstroTech Ritchey-Chretien truss tube telescope, a Takahashi EM-400 mount, and a QSI 683 mono CCD camera with a full compliment of filters.

Horsehead and Flame Nebulae

Great Orion Nebula

Flame Nebula in Orion with Narrowband filters

The telescope has a 2,432mm focal length at f8, a bit shorter
and faster with the flattener, and 12-inch light gathering capability. The monochromatic CCD
camera has a full frame 8.3MP sensor and a built in cooling mechanism that will
cool the sensor down to -40 degrees Celsius to minimize noise. An integrated 8-position filter wheel allows me to decide whether to shoot with standard color filters (L, R, G, & B) or add narrowband filters (H-Alpha, Sulfur II, and Oxygen III) to bring out colors in a very narrow band of light that can be used to create what is commonly referred to as a Hubble palette.

Takahashi EM-400 mount

Finally, while AstroPhysics may be the Mercedes Benz of astronomy gear, Takahashi equipment is its Japanese counterpart much like what Lexus is to Mercedes. The Takahashi EM-400 mount is a favorite of many astro imagers, tracking and slewing like a well oiled machine. All in all, I've been very pleased with the combination of the AstroTech Ritchey and the Tak EM-400 mount. Here are more examples of what the rig can do.

Cone, Christmas Tree, and Fox Fur Nebulae

Eagle Nebula (with narrowband filters)

Sombrero Galaxy, an example of an edge on galaxy orientation

Western Veil Nebula, aka the Witch's Broom

Pinwheel Galaxy, an example of a full front galaxy orientation

Part VI - Cameras

Next up is a discussion on astrophotography cameras where I'll walk you through the world of CCD cameras, including CCD one shot color models, monochromatic versions, and filters.

So, and what about the field of view on the "Horsehead and Flame Nebulae" with the QSI 683 and the 12” AstroTech Ritchey-Chretien ... how on earth can you get that field of view with that setup ???? This is not adding up ... would you care to elaborate on this inconsistency ?